Magnesium's principle function in the body is in the regulation of enzyme activity as well as directly stimulating some enzyme systems. Mg defiiciency is known to cause low blood potassium and calcium and to result in neuromuscular hyperexcitability and cardiac arrhythmias. It is also linked to hypertension, artherosclerotic vascular disease, sudden death, and osteoporosis. This study will involve families with renal Mg wasting, which is usually associated with a variety of medications and/or the disorders of diabetes mellitus and alcoholism.